This invention relates to soldering apparatus and is particularly concerned with systems in which components to be coated with solder are passed through a bath of solder. The invention is particularly, but by no means exclusively, concerned with applying solder to the leads of integrated circuit packs such as dual-in-line (DIP), SOIC or other types.
Frequently, such coating is carried out in a wave soldering system. In such a system a carrier for the components may be passed over a bath of solder in which a standing wave if formed. The arrangement is such that the component portions to be coated pass through the peak of the standing wave of solder as the carrier is moved over the bath.
A problem with certain known systems is that it is difficult to control the quality of the coating, particularly as regards an even thickness. Frequently, package leads have regions where the coating is significantly thicker than elsewhere. Another problem is that of accommodating various different types of components which may be handled, particularly as regards the depth of immersion in the wave of solder. For example, a DIP may require immersion to a depth of 6 mm whereas an SOIC--designed for surface mounting on a circuit board--may require a depth of e.g. only 1.2 mm. To cope with such a range of depths it may be necessary to change the wave height or even to use separate apparatus dedicated to the individual components.
There had been proposed a system for dipping individual carriers vertically into and removing them vertically out of a bath of solder. This provides an improvement in quality over wave soldering apparatus but has the disadvantage of being considerably slower since carriers cannot be processed continuously.
There is thus a need for a system which will achieve some of the benefits of both wave soldering and dip soldering so as to provide both reasonable quality and reasonable speed of operation, and preferably greater versatility.